1. Technical Field
The present invention relates to an optical device that guides image light, an image display apparatus, and a method for manufacturing the optical device.
2. Related Art
A variety of display apparatus each of which is worn around the head for use and guides video image light from a display device through a light guide member to the eyeballs of a viewer, such as a head-up display, and a view finder of a video camcorder or any other imaging apparatus, have been proposed. One of the display apparatus of this type has a spectacle-like exterior appearance. For example, the display apparatus disclosed in JP-T-2003-536102 can reflect an image on a liquid crystal display toward the eyes of a viewer by using internal reflection and a plurality of transflective surfaces for image information observation.
A display apparatus of this type is, for example, specifically configured as follows: The display apparatus has a spectacle-like exterior appearance in which a substrate positioned in front of the eyes of a viewer is supported by temples hooked on the ears of the viewer; image light outputted from a display device, such as a liquid crystal display, built in each of the temples passes through an optical system in the temple in such a way that diffused light from each position on the display device is converted info a parallelized light flux; the parallelised light flux is then incident on the substrate and totally reflected off a prism reflection surface of the substrate; the totally reflected light flux then travels through the substrate while undergoing internal reflection; and the light flux is guided to an eyeball of the viewer via a plurality of transflective surfaces.
In the display apparatus disclosed in JP-T-2003-536102 described above, however, light outputted from the center of the display device is guided as the parallelized light flux through the substrate depending on the positions where a light source, the optical system in the temple, and other components are located and angles at which the prism reflection surface and transflective surfaces are set in the substrate, whereas light outputted from a position set apart from the center of the display device is first guided as the parallelised light flux but the prism reflection surface and the transflective surfaces change part of the parallelised light flux to a non-parallelised light flux having an angle different front an intended angle. Since the angle of the light guided through the substrate corresponds to the position of a light spot in the image light visually recognized by the viewer, the light having the angle different from an intended angle is disadvantageously recognised by the viewer as an inappropriate light spot that is what is called a ghost spot.